• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.10
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• pp.522-531
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• 2001

A large dispersion value in optical fiber cable should be maintained to suppress the nonlinear effect induced distortion for the narrow channel spaced DWDM system while small value of dispersion is needed for high bit rate transmission. To meet these two requirement simultaneously, dispersion distribution control method during the cabling process was exploited. And dispersion distribution cable was fabricated by the way of designing alternation sections in single cable piece with standard single mode fiber(SSMF) and newly developed negative dispersion fiber(NDF). It is shown that the discretely dispersion varying cable along the axis keep the same average dispersion value of an entire cable length as that of nonzero dispersion shifted fiber(NZDSF) with 3.6 ps/km/nm while the local dispersion is around 17 ps/km/nm of absolute value. Moreover, the developed cable had good optical and mechanical properties and the feasibility of this cable for practical use was confirmed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.3
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• pp.244-252
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• 2004

The theoretical method is developed to investigate the vibration characteristics for the partially fluid-filled continuous cylindrical shells with the intermediate supports. The intermediate supports are simulated by two types of artificial springs : the translational spring for the translation for each direction and the rotational spring for a rotation. The springs are continuously distributed along the circumferential direction. By allowing the spring stiffness to become very high compared to the stiffness of the structure, the rigid intermediate supports are approximated. In the theoretical procedure, the Love's thin shell theory is adopted to formulate the theoretical model. The frequency equation of the continuous cylindrical shell is derived by the Rayleigh-Ritz approach based on the energy method. Comparison and convergence studies are carried out to verify and establish the appropriate number of series term and the artificial spring stiffness to produce results with an acceptable order of accuracy. The effect of intermediate supports, their positions and fluid level on the natural frequencies and mode shapes are studied.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2004-2012
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• 2014

Energy storage devices are necessary to obtain stable utilization of renewable energy sources. When black-out occurs, distributed renewable power sources with energy storage devices can operate under standalone mode as uninterruptable power supply. This paper proposes a dynamic response analysis with small-signal modeling for the standalone operation of a photovoltaic power generation system that includes a bidirectional charger/discharger with a battery. Furthermore, it proposes a DC-link voltage controller design of the entire power conditioning system, using the storage current under standalone operation. The purpose of this controller is to guarantee the stable operation of the renewable source and the storage subsystem, with the power conversion of a very efficient bypass-type PCS. This paper presents the operating principle and design guidelines of the proposed scheme, along with performance analysis and simulation. Finally, a hardware prototype of 1-kW power conditioning system with an energy storage device is implemented, for experimental verification of the proposed converter system.

• Earthquakes and Structures
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• v.9 no.4
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• pp.911-936
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• 2015

This work evaluates the performance of a number of seismic assessment procedures when applied to a case study reinforced concrete (RC) wall building. The performance of each procedure is evaluated through its ability to accurately predict deformation demands, specifically, roof displacement, inter-storey drift ratio and wall curvatures are considered as the key engineering demand parameters. The different procedures include Direct Displacement-Based Assessment, nonlinear static analysis and nonlinear dynamic analysis. For the latter two approaches both lumped and distributed plasticity modelling are examined. To thoroughly test the different approaches the case study building is considered in different configurations to include the effects of unequal length walls and plan asymmetry. Recommendations are made as to which methods are suited to different scenarios, in particular focusing on the balance that needs to be made between accurate prediction of engineering demand parameters and the time and expertise required to undertake the different procedures. All methods are shown to have certain merits, but at the same time a number of the procedures are shown to have areas requiring further development. This work also highlights a number of key aspects related to the seismic response of RC wall buildings that may significantly impact the results of an assessment. These include the influence of higher-mode effects and variations in spectral shape with ductility demands.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.171-182
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• 2018

For the first time, nonlocal damped vibration and buckling analyses of arbitrary tapered bidirectional functionally graded solid circular nano-plate (BDFGSCNP) are presented by employing modified spectral Ritz method. The energy method based on Love-Kirchhoff plate theory assumptions is applied to derive neutral equilibrium equation. The Eringen's nonlocal continuum theory is taken into account to capture small-scale effects. The characteristic equations and corresponding first mode shapes are calculated by using a novel modified basis in spectral Ritz method. The modified basis is in terms of orthogonal shifted Chebyshev polynomials of the first kind to avoid employing adhesive functions in the spectral Ritz method. The fast convergence and compatibility with various conditions are advantages of the modified spectral Ritz method. A more accurate multivariable function is used to model two-directional variations of elasticity modulus and mass density. The effects of nanoscale, in-plane pre-load, distributed dashpot, arbitrary tapering, pinned and clamped boundary conditions on natural frequencies and buckling loads are investigated. Observing an excellent agreement between results of current work and outcomes of previously published works in literature, indicates the results' accuracy in current work.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.4
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• pp.73-81
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the compaction and compressive strength properties of stress-strain, elastic modulus and fracture mode CSG materials reinforced polypropylene fiber. Polypropylene fiber widely used for concrete reinforcement is randomly distributed into cemented sand. The two types of polypropylene fiber (monofillament and fibrillated fiber) were used and fiber fraction ratio was 0, 0.2 %, 0.4 %, 0.6 % and 0.8 % by the weight of total dry soil. The effect of fiber fraction ratio and fiber shape on compaction and compressive strength were investigated. The optimum moisture contents (OMC) of CSG material increased as fiber fraction increased and the dry density of CSG material decreased as fiber fraction. Also, the maximum increase in compressive strength was obtained at 0.4 % content of monofillament and fibrillated fiber. CSG material behaviour was controlled not only by fiber fraction but also fiber distribution, fiber shape and fiber type.

• The Journal of the Korea Contents Association
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• v.2 no.2
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• pp.36-41
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• 2002

In a mediator based information integration system that integrates information distributed on various data sources as a common data model, there are many researches on a common data mode providing a reservation of integrated data semantic, and on a resolution for a conflict caused by integrating various data modes. This paper proposes the DataBlender system that minimizes the semantic losses and provides an easy resolution for a conflict using the XML technology like as XML Schema, XQuery. Futhermore, it provides an integrated query facility usable in the mobile environment. So it becomes a foundation for a next Internet business environment.

• Structural Engineering and Mechanics
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• v.32 no.4
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• pp.517-529
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• 2009

A passive vibration mitigation architecture is proposed to damp transverse vibrations of guyed masts. The scheme is based on a number of pendula attached to the mast and tuned to the vibration modes to be controlled. This scheme differs from the well-known autoparametric pendulum absorber system. The equations of motion of the guyed mast with an arbitrary number of pendula are obtained. The leading bending behaviour of a typical truss mast is described by an equivalent beam model whereas the guys are conveniently modeled as equivalent transverse springs whose stiffness comprises the elastic and geometric stiffness. By assuming a mast with an inertially and elastically isotropic cross-section, a planar model of the guyed mast is investigated. The linearization of the equations of motion of the mast subject to a harmonic distributed force leads to the transfer functions of the structure without the dampers and with the dampers. The transfer functions allow to investigate the mitigation effects of the pendula. By employing one pendulum only, tuned to the frequency of the lowest mode, the effectiveness of the passive vibration potential in reducing the motion and acceleration of the top section of the mast is demonstrated.

• Journal of KIISE:Information Networking
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• v.28 no.4
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• pp.508-516
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• 2001

This paper proposes multicast routing algorithm that operates for non-interactive multimedia applications such as VOD(Video On Demand) and real-time data broadcasting. It is possible that there exist multiple senders in non-interactive multimedia applications. This paper designs multicast routing algorithm in this environment. The simulation of algorithm proposed in this paper shows much better performancetcost, delay) than that of only one source. To guarantee the performance of algorithm, Broadband ATM network is modelled in simulation.

• Animal Systematics, Evolution and Diversity
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• v.21 no.2
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• pp.259-272
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• 2005

The antipatharians in Korea were known with three species and two genera belonging to family Antipathidae. In the present study, three species, Antipathes densa, A. grandiflora, and A. dubia, have been newly recorded to Korean antipatharian fauna with the samples collected from Jeju-do during the period from 2003 to 2005. The description was mainly based on the habitat, the branching mode of corallums, the size and arrangement of polyps and spines on the axis, and also the types of cnidae. They had three kinds of cnidae: spirocyst, basitrich, and microbasic p-mastigophore. Spirocysts and basitrichs were distributed at tentacles and microbasic p-mastigophores were mainly at septal filaments.